Weather stations typically include one or more sensors in a housing protected by shielding. Met One Instruments (Grants Pass, Oreg.) sells radiation shields including an aspirated radiation shield for temperature and humidity sensors. U.S. Pat. No. 6,247,360, incorporated herein by this reference, discloses an aspirated radiation shield for weather sensors. See also U.S. Pat. No. 5,591,907 incorporated herein by this reference.
The measurement of ambient air temperature can be erroneously effected by solar radiation impinging on a temperature measurement probe, contamination of the probe by dirt, frost and moisture, and by ambient wind modifying the airflow over the measurement probe. Present shields, even aspirated shields, may still produce erroneous results when fan motors fail; when dirt, frost, or moisture collects on the temperature probes; or when high winds create a Bernoulli Effect vacuum that substantially reduces the airflow into the shield and hence over the temperature measurement probe.